The primary goal of this study is to evaluate the clinical consistency, as measured by safety, tolerability, and immunogenicity, of three production lots of DTaP when administered to healthy infants at 2,4, and 6 months of age. The secondary goal is to compare the safety and immunogenicity of the production lots of Biocine DTaP with that of a development lot of Biocine DTaP used in an Italian efficacy study, when administered to healthy infants at 2, 4, and 6 months of age.